The chemistry of the process is based principally on the technique of production of the alkali metals by thermal processes. An excellent review of the techniques for the thermal production of the alkali metals by reduction of an appropriate combination of the compounds of the alkali metals with a reducing agent is given on pages 308 through 327 of "Mellors Comprehensive Treatise on Inorganic and Theoretical Chemistry," Vol. 2, Supplement 2, Longman's, Green and Company, Ltd., London, 1961, (John Wiley & Sons Incorporated, New York). Further information on the chemistry of the thermal production of the alkali metals from their compounds is given in "Comprehensive Inorganic Chemistry," M. C. Sneed and R. C. Braested, Vol. 6, 1957, D. VanNostrand Company, Princeton, New Jersey and also in "The Encyclopedia of Chemical Reactions," by C. A. Jacobson, Rheinhold Publishing Corporation, New York, 1956.
Much of the useful information referred to in these encyclopedic compendia is covered more specifically in various issued patents as follows:
U.s. pat. No. 1,837,935 PA1 British Pat. No. 466,763 PA1 British Pat. No. 486,930 PA1 U.s. pat. No. 2,162,619 PA1 U.s. pat. No. 2,391,728 PA1 U.s. pat. No. 2,685,346 PA1 U.s. pat. No. 2,774,663 PA1 U.s. pat. No. 2,789,047 PA1 U.s. pat. No. 2,810,636
The prior art defined in this background information deals principally with the thermal production of sodium, the production of combustible gases which may be utilized specifically as a source of thermal energy being incidental to the process. While many dozens of processes involving an equal number of variations in chemistry for thermal production of sodium are described in the prior art, the particular procedures which appear to have been emphasized are those which involve the reduction of a compound of sodium with either carbon or metallic iron. In some cases, a minor amount of metallic iron, usually of the order of 2 percent of the carbon is added along with the carbon to catalyze the reduction process. It is further recognized in the prior art that in order to prevent adverse back reactions between the metallic sodium and the carbon monoxide produced that the products of the reaction must be removed rapidly from the reaction zone and cooled quickly to prevent the adverse back reaction which detracts from the efficiency of the process. Other claimed adverse back reactions include the reaction of the alkali hydroxide with carbon monoxide to produce the carbonate of the alkali metal, an undesired reaction if the function of the reaction is the production of metal. In addition, the excessive temperatures at which the prior art reactions are carried out produces significant portions of the sodium compounds used as the source of the metallic sodium in sublimed or gaseous form which then pass through the reaction zone and are condensed along with the metallic sodium produced, thereby not only again detracting from the efficiency for the reaction for the production of sodium but also producing an impure production of metallic sodium contaminated with very substantial quantities of compounds of sodium which have to be subjected to specialized and expensive treatments requiring recycling in order to produce commercially effective yields of metallic sodium.
Procedures described in the prior art involve the requirement for rapid removal of the products of the reaction from the reaction vessel coupled with shock cooling to reduce the back reaction between metallic sodium, volatilized compounds of metallic sodium and carbon monoxide which detract from the efficiency of production of the thermally produced metallic sodium. Techniques for alleviating these difficulties at least to a partial extent have been the utilization of reactors operating under reduced pressure or by sweeping the reaction zone with dry hydrogen, coupled with shock cooling of the sodium metal produced.
Typical of some of the problems encountered in the thermal production of sodium through prior art procedures are the disclosures given in U.S. Pat. Nos. 2,774,663 and 2,810,636 in which cyclic processes for the production of sodium are described involving the formation of an excessive amount of dross, usually in the form of sodium carbonate, which is collected along with the sodium coupled with the volatilization of sodium hydroxide and the need for the addition of extra amounts of sodium hydroxide to the sodium carbonate containing sodium in order to produce a molten mixture which can be recycled. In carrying out this recycling in the manner described in the aforementioned patents sodium carbonate is again produced which has, again, to be reacted over again, thereby again detracting from the efficiency of the reaction by virtue of the requirement of the need for excessive amounts of heat needed to reduce much more reagent than is necessary.
Though an overall recovery of more than 90 percent is claimed these processes could not be considered as efficient producers of carbon monoxide and hydrogen in view of the excessive amount of heat required for such products due to the need for recycling of reagents in an undesired manner by overly expensive procedures.